Alzheimer's disease (AD) is a disorder that causes the gradual loss of brain cells. AD is named after Dr. Alois Alzheimer, who in 1906 noticed changes in the brain tissue of a woman who had died of an unusual mental illness. Upon examination, Dr. Alzheimer found abnormal clumps and tangled bundles of fibers, which are now known as amyloid plaques and neurofibrillary tangles, respectively. Today, these plaques and tangles in the brain are considered hallmarks of AD.
AD results in damage in brain regions associated with thought, memory, and language. Symptoms of AD are progressive and include dementia, which includes characteristics such as loss of memory, problems with reasoning or judgment, disorientation, difficulty in learning, loss of language skills, and decline in the ability to perform routine tasks. Additional AD symptoms may include personality changes, agitation, anxiety, delusions, and hallucinations.
The risk of AD in the population increases with age. It is believed that up to 4 million Americans have AD. The onset of AD is generally after age 60, but in rare instances younger individuals may be afflicted. It is generally believed that approximately 3 percent of men and women ages 65 to 74, and almost half of those age 85 and older have AD.
There is as yet no clear understanding of the cause of AD. Age is a known risk factor and there is some association between family history and early-onset AD. Although a pattern of decline in AD patients is generally clinically recognizable as the disease progresses, reliable diagnostic methods are lacking. The only definitive diagnostic test for AD at this time is to determine whether amyloid plaques and tangles are present in a subject's brain tissue, a determination that can only be done after death. Thus, due to the lack of suitable diagnostic methods, health-care professionals are only able to provide a tentative diagnosis of AD in an individual, particularly at the early to mid stages of the disease. Although these diagnoses can indicate that a person “likely” has AD, the absence of a definitive diagnosis reflects a critical need for more accurate and reliable AD diagnostic tests.
In addition to the absence of reliable diagnostic methods, the are also very limited treatment options available for patients suspected of having and/or diagnosed as having AD. Several drugs have been approved in the US for treatment of early and mid-stage AD, but they have significant detrimental side effects and limited efficacy. The lack of effective treatments for AD means that even with a diagnosis of probable AD, the therapeutic options are quite limited. Thus, there is a significant need for effective compounds and methods for preventing and/or treating AD.